Linear actuator assembly

ABSTRACT

A linear actuator assembly having a cylinder body and an actuator rod slideably disposed in the cylinder body. The actuator rod has a forward end portion exterior of the cylinder body. An end plug is connected the cylinder body and closes an end portion of the cylinder body. A first retaining member is coupled to the actuator rod and is connectable to a first mounting portion to allow the actuator rod to pivot. A second retaining member removably engages the end plug and the rear end portion of the cylinder body. The second retaining member is connectable to the second mounting portion to allow the cylinder body to pivot about the second retaining member relative to the second mounting portion. The second retaining member retains the end plug within the rear end portion of the cylinder. The end plug can be removed from the cylinder body upon disengagement of the second retaining member from the end plug.

TECHNICAL FIELD

This application relates to actuators, and more particularly to linearactuator assemblies.

BACKGROUND

Conventional personnel lifts and other heavy equipment often usehydraulic or pneumatic linear actuators to control portions of theequipment. FIG. 1 is an isometric view of a conventional hydrauliclinear actuator of the type used with personnel lift equipment. Thelinear actuator 1 has a cylinder 2, a piston rod 3 that moves axially inand out of the cylinder, and rigid pivot mounts 4. The rigid pivotmounts are short sections of tube welded onto the cylinder and the rodand precision machined to accept bushings that are added during theassembly of the linear actuators. Other components of the linearactuator are welded together during the assembly process such that thelinear actuator is referred to as having a welded construction.

This welded construction of the conventional linear actuator has severalfabrication drawbacks or disadvantages. The welding process impartsinternal material stresses that can cause distortion in the componentsbeing welded. For example, the cylinder tube may distort or warp to anout-of-round condition when subjected to the welding process. As aresult, the internal bore of the cylinder tube may need to bere-machined, honed and/or polished, thereby adding to the cost of theassembly. Welds are also susceptible to stress corrosion cracking, whichmay result in leakage and loss of hydraulic fluid. The stress corrosioncracking also limits the repair options to those that do not involvere-welding the damaged area, because the heat from additional weldingmay damage internal bearings, bushings, or seals. The additional weldingcan also impart component distortion, which may result in binding orexcessive wear during component distortion, which may result in bindingor excessive wear during operation of the linear actuator. The weldedconstruction also greatly limits the ability to substantiallydisassemble the linear actuator, or the ease with which it can be done,such as for maintenance, repair, or service of some of the components.

The linear actuator may also be susceptible to binding if great care isnot taken during the manufacturing process to achieve proper alignmentof the components. For example, each of the rigid pivot mounts welded tothe cylinder and actuator rod is configured to receive a mounting pinthat secures the linear actuator to the equipment, while allowing thecylinder and/or piston rod to pivot relative to the device to which therespective pivot mount is attached. The piston rod and the cylinder,however, only move linearly relative to each other. Accordingly, therigid pivot mounts must be welded or otherwise securely connected in aperpendicular orientation relative to the cylinder and/or the pistonrod.

Misalignment of the rigid pivot mounts and/or mating structure mountscan result in misalignment and binding between the cylinder and thepiston rod during the rod's linear stroke. Such a construction processis labor-intensive, time-consuming, and requires relatively forgivingtolerances that accommodate for some misalignment during manufacturing.Failure to allow for misalignment may also result in the linear actuatorassembly experiencing significant adverse physical stresses, resultingin poor performance, bearing and/or seal failure, and perhaps shortenedcomponent life.

Conventional linear actuators typically also utilize several bushingsand bearing assemblies between moving components. For example, linearactuators typically include front and rear cylinder pivot bushings, andinternal bearings in the cylinder, to facilitate axial movement of theactuator rod. Dual-direction actuators also typically utilize a frontgland bushing to facilitate axial movement of the actuator rod relativeto a front gland. These bushings and bearings are additional componentsthat must be properly assembled in the linear actuator during theassembly process, thereby adding to the complexity and cost ofmanufacturing a conventional linear actuator. The bushings and bearingsare also additional components that can be subjected to stresses andexcessive wear if proper alignment is not maintained in the linearactuator.

Linear actuators often utilize complex couplers to try to compensate forsome misalignment between the moving components of the linear actuator.For example, a conventional coupler can have a first part fixedlyattached to an end of the actuator rod. A second part of the coupler isattached to the first part with a joint structure or other relativelycomplex mechanism that allows the second part to move relative to thefirst part to compensate for some misalignment in the linear actuator.These couplers add to the weight, complexity, required installationspace and cost of manufacturing the linear actuators.

Conventional hydraulic and pneumatic linear actuators are also typicallycontrolled by the flow of fluid to and from the actuators via conduits.The flow rate, direction, pressure, etc., of the fluid is typicallycontrolled by a plurality of valves in a manifold or otherwise mountedremotely from the linear actuator. However, this valve arrangement hasdrawbacks. The greater the distance between the control valve or valvesand the actuator, the slower will be the actuators' motion response.This is due to the compressibility of the fluid contained within theconduits that connect the valves to the actuator. For example, when anoperator activates one or more valves to control the fluid that movesthe linear actuator there is a proportional time delay till the actuatoractually moves.

Another drawback of the valve manifold arrangement is its complexity. Ifone of several linear actuators is not operating correctly, due to acontrol valve problem, the process to identify the malfunctioning valveamong many within a single manifold block can be problematic and timeconsuming, which increases the amount of time that the vehicle or otherunit is out of service. Accordingly, there is a need for an improvedlinear actuator assembly.

SUMMARY

The present invention provides a linear actuator assembly that overcomesdrawbacks experienced in the prior art and provides additional benefits.In one embodiment, a linear actuator assembly is connectable to firstand second mounting portions. The linear actuator assembly comprises acylinder body having an interior area and a rear end portionpositionable adjacent to the second mounting portion. An actuator rod isslideably disposed in the cylinder body. The actuator rod has a forwardend portion exterior of the cylinder body and is positionable adjacentto the first mounting portion. An end plug closes the rear end portionof the cylinder body.

A first retaining member is coupled to the forward end portion of theactuator rod and is connectable to the first mounting portion to allowthe actuator rod to pivot about the first retaining member relative tothe first mounting portion. A second retaining member removably engagesthe end plug and the rear end portion of the cylinder body. The secondretaining member is connectable to the second mounting portion to allowthe cylinder body to pivot about the second retaining member relative tothe second mounting portion. The second retaining member retains the endplug within the rear end portion of the cylinder. The end plug can beslideably removed from the cylinder body upon disengagement of thesecond retaining member from the end plug.

Another embodiment provides an a linear actuator assembly connectable tofirst and second mounting portions, the first mounting portion beingmoveable relative to the second mounting portion. The assembly has acylinder body with an interior area and a rear end portion positionableadjacent to the second mounting portion. An actuator rod is moveablydisposed in the cylinder body. The actuator rod has a forward endportion exterior of the cylinder body and positionable adjacent to thefirst mounting portion. An end plug is connected to the rear end portionof the cylinder body. The end plug has a weldless interface with thecylinder body and closes the rear end portion of the cylinder body. Afirst retaining member is coupled to the forward end portion of theactuator rod and is connectable to the first mounting portion to allowthe actuator rod to pivot about the first retaining member relative tothe first mounting portion. A second retaining member removably engagesthe end plug and is connectable to the second mounting portion to allowthe cylinder body to pivot about the second retaining member relative tothe second mounting portion, wherein the end plug can be removed fromthe cylinder body.

Another embodiment provides an articulatable assembly, comprising firstand second members articulatable relative to each other. The firstmember has a first mounting portion and the second member has a secondmounting portion. An actuator assembly is connected to the first andsecond members. The actuator assembly comprises a cylinder body havingan interior area, and a shaft disposed in the cylinder body. The shafthas a free end portion exterior of the cylinder body. An end plug isremovably connected to the cylinder body and plugs a portion of theinterior area.

A first retaining member is coupled to the free end portion of the shaftand connected to the first mounting portion. The first retaining memberis configured to allow the shaft to pivot relative to the first mountingportion about a longitudinal axis of the first retaining member. Asecond retaining member removably retains the end plug in the portion ofthe cylinder body. The second retaining member is connected to thesecond mounting portion and is configured to allow the cylinder body topivot relative to the second mounting portion about a longitudinal axisof the second retaining member. The end plug can be removed from theportion of the cylinder body upon disengaging the second retainingmember from the end plug. The foregoing and other aspects of theinvention will now be described in more detail with reference to theaccompanying drawings. This Summary section is provided to introduce ina simplified manner aspects and features further described below in theDetailed Description section and illustrated in the figures. ThisSummary section is not intended to limit the scope of the claimedsubject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a conventional hydraulic linear actuatorassembly.

FIG. 2 is an isometric view of a linear actuator assembly in accordancewith an embodiment of the present invention.

FIG. 3 is an isometric view of the linear actuator assembly of FIG. 2shown with spacers and mounting pins.

FIG. 4 is a cross-sectional view of the linear actuator assembly of FIG.2 taken substantially along lines 4-4.

FIG. 5 is an isometric view of a piston rod shown removed from thelinear actuator assembly of FIG. 2.

FIG. 6 is an enlarged cross-sectional view of a front end portion of thelinear actuator assembly of FIG. 4.

FIG. 7 is a side elevation view of a front end portion of a linearactuator assembly in accordance with another embodiment.

FIG. 8 is a cross-sectional view of the front end portion of the linearactuator assembly taken substantially along lines 8-8 of FIG. 7.

FIG. 9A is an enlarged cross-sectional view of a rear end portion of thelinear actuator assembly of FIG. 4 with an internal valve in a closedposition.

FIG. 9B is an isometric view of a rear end portion of a linear actuatorassembly in accordance with another embodiment.

FIG. 9C is a cross-sectional view of the rear end portion of the linearactuator assembly taken substantially along lines 9C-9C.

FIG. 9D is an isometric view of the end plug shown removed from thecylinder of the linear actuator assembly of FIG. 9B.

FIG. 10 is an enlarged side elevation view of an end plug shown removedfrom the linear actuator assembly of FIG. 9.

FIG. 11 is an isometric view of a poppet of an internal valve shownremoved from the end plug of the linear actuator assembly of FIG. 10.

FIG. 12 is a cross-sectional view of the rear end portion of the linearactuator assembly of FIG. 9 with the internal valve in an open position.

FIG. 13 is an isometric view of a linear actuator assembly in accordancewith another embodiment of the present invention.

FIG. 14 is a cross-sectional view of the linear actuator assembly ofFIG. 13 taken substantially along lines 14-14.

FIG. 15 is an enlarged cross-sectional view of the forward portion ofthe linear actuator assembly of FIG. 14.

FIG. 16 is a cross-sectional view of a linear actuator assembly withformed-in-place seals in accordance with another embodiment of thepresent invention.

FIG. 17 is an isometric view of a vehicle having at least one linearactuator assembly in accordance with an embodiment of the presentinvention.

DETAILED DESCRIPTION

Embodiments of the present invention include linear actuator assemblies,including hydraulic linear actuators and pneumatic linear actuators,along with methods for using the actuators. Several specific details ofthe invention are set forth in the following detailed description and inFIGS. 2-17 to provide a thorough understanding of embodiments of theinvention. One skilled in the art, however, will understand that thepresent invention may have additional embodiments, and that otherembodiments of the invention may be practiced without one or more of thespecific features described below. In other instances, well-knownstructures, materials, or operations are not shown or described in orderto avoid obscuring aspects of the invention.

FIG. 2 is an isometric view of a linear actuator assembly 10 inaccordance with an embodiment of the present invention. The linearactuator assembly 10 is a ram-style actuator having an actuator rod 12slideably disposed at least partially within a cylinder 14. The actuatorrod is shown in a retracted position and is movable relative to thecylinder between extended and retracted positions. The cylinder issealably closed without the use of welding at its rear end portion 16 byan end plug 90. A valve system 20 extends through the rear end portionof the cylinder and one or more valves 22 may be disposed in the endplug. The valves are configured to control the flow of a driving fluid,such as hydraulic or pneumatic fluid, that controls the movement of theactuator rod relative to the cylinder between the extended and retractedpositions.

The linear actuator assembly 10 of the illustrated embodiment isconfigured such that neither the cylinder nor the actuator rod issubjected to welding during the manufacturing and/or assembly process.In other words, none of the components are welded together during theassembly of the linear actuator. Accordingly, the linear actuatorassembly can be of non-welded construction. This non-welded constructionprovides significant benefits. By not welding the components together,the components are not subject to distortion, warping, or other sideeffects of welding. Thus, the cylinder and/or actuator rod do notrequire secondary machining, honing, or polishing to correct for theside effects of welding in an effort to maintain proper alignment andoperation of the components of the assembly. Post assembly distortiondue to retained weld stress is eliminated. The non-welded constructionis significantly less labor-intensive, thereby significantly reducingthe manufacturing cost of the linear actuator assembly. Other,non-metallic materials can also be employed. This construction can alsoallow the assembly to be easily and quickly disassembled and/orreassembled as needed for service and maintenance. As discussed ingreater detail below, the linear actuator assembly is configured so thatit has fewer parts, is much easier to assemble and disassemble, islighter, has a lower profile, and is easier to maintain and/or repairthan a conventional linear actuator assembly. The linear actuatorassembly is also configured so that the cylinder and the actuator rodare automatically held together and in alignment upon mounting theassembly via the mounting pins to a structure (e.g., a lift assembly)that will be moved via the actuator assembly. Accordingly, additionalcomponents used to hold conventional linear actuator assemblies togetherare eliminated, thereby reducing the complexity, weight, size, and costof the linear actuator assembly.

The linear actuator assembly 10 of the illustrated embodiment alsoincludes an aperture 24 that extends through the rearward end of thecylinder and through the end plug substantially perpendicular to thelinear actuator's longitudinal axis 32. The aperture pivotably receivesa mounting pin 26 (shown in phantom lines) that securely mounts to aportion of the equipment or device onto which the linear actuatorassembly is mounted. The opposite end of the linear actuator assemblyincludes an aperture 28 extending through a front end portion 30 of theactuator rod substantially perpendicular to the linear actuatorassembly's longitudinal axis. The aperture in the actuator rod pivotablyreceives another mounting pin 26 that attaches the front end of thelinear actuator assembly to another portion of the equipment or deviceonto which the linear actuator assembly is mounted. The perpendicularorientation of the apertures 24 and 28 relative to the longitudinal axesof the cylinder and the actuator rod is relatively easy to achieveduring the manufacture of the components, thereby substantially avoidingthe risk of binding due to misalignment of the cylinder and/or theactuator rod.

In one embodiment illustrated in FIG. 3, the linear actuator assembly 10can include front spacers 34 that extend over the forward mounting pin26 and are positioned adjacent to the front end portion 30 of theactuator rod 12. Rear spacers 36 can also be provided that extend overthe rear mounting pin and are positioned on opposite sides of the rearend portion of the cylinder. The front and rear spacers of theillustrated embodiment are shaped and sized so a conventional U-joint(not shown) used on equipment can be mounted to the forward and rearmounting pins and properly oriented relative to the front and rearportions of the linear actuator assembly. The spacers prevent unwantedlateral motion of the linear actuator assembly relative to theconventional U-joint. In other embodiments, different sized spacers canbe used for fitting the linear actuator assembly into place on aselected piece of equipment or device. In other embodiments, as shown inFIG. 2, spacers are not provided when not needed.

FIG. 4 is a cross-sectional view taken substantially along line 4-4 ofFIG. 2 showing the actuator rod 12 in the retracted position relative tothe cylinder 14. The cylinder of the illustrated embodiment is a tubularmember having a front end portion 38 opposite the rear end portion 16.The cylinder has an interior area 40 defined by an inner surface 42,which has a substantially constant inner diameter (ID). The cylinder issized such that, when the actuator rod is in the fully retractedposition, as shown in FIG. 4, a front end 44 of the actuator rod isexterior of the cylinder's interior area. The inner diameter of thecylinder substantially corresponds to the outer diameter (OD) of theactuator rod such that the actuator rod can slide along the innersurface of the cylinder as the actuator rod moves axially between theretracted and extended positions.

The cylinder of the illustrated embodiment is constructed of a machinedand polished metal tube capable of withstanding the pressures generatedby the driving fluid within the interior area without any substantive orplastic deformation of the tube's cylindrical shape. The cylinder can bemachined or otherwise formed to provide a straight, round, and smoothinside surface. As indicated above, the linear actuator assembly isconstructed so that none of the actuator's components are welded to thecylinder, thereby avoiding the heat, warping, distortion, or otherdrawbacks experienced by the prior art. The cylinder of the illustratedembodiment can be made of steel, alloys, or other suitably durablematerial.

FIG. 5 is an isometric view of the actuator rod 12 shown removed fromthe linear actuator assembly 10 of FIG. 4. The illustrated actuator rodis a rigid member, such as a metal rod, having a substantially constantouter diameter, such that the actuator rod's outer surface 46 slidesalong the inner surface of the cylinder (FIG. 4), and the inner surfaceof aperture 56 pivots about the external surface of pin 26. The actuatorrod of the illustrated embodiment has a bearing surface coating 46 thatslides against the inner surface of the cylinder (FIG. 4), and the outersurface of pivot pin 26 (FIG. 5) without substantial frictional losses.In the illustrated embodiment, the bearing surface coating 46 isprovided by coating a steel rod and rod aperture 56 with a lubriciousmaterial 48, such as an electroless nickel plus thirty percent Teflon(i.e., PTFE) impregnation. In another embodiment, the inside surface ofthe cylinder 14 (FIG. 4) and the exterior surface of pivot pin 26 (FIG.5) may be provided with a coating of the lubricious material, and in yetanother embodiment, the actuator rod 12, pivot pin 26 and the cylinder14 can be provided with a coating of the lubricious material. Thecoating provides corrosion protection and provides a low frictionbearing surface along the length of the actuator rod that remains withinthe cylinder. Accordingly, the linear actuator assembly of theillustrated embodiment is a bearingless assembly, because additionalbearing components are not used between the actuator rod and thecylinder while still allowing for smooth, efficient, and effective axialmovement of the actuator rod within the cylinder 14 (FIG. 4), andpivotal motion between rod aperture 56 and pivot pin 26 (FIG. 5) underworking loads.

While the above embodiments use a coating impregnated or otherwiseapplied to the outside of a shaft (e.g., the actuator rod), or theinside of the cylinder, or both, other coating materials, impregnationprocesses, or materials of the rod can be used to achieve the lowfriction engagement between a shaft and the cylinder, therebyeliminating the need for additional bearing assemblies. This bearinglesslinear actuator assembly 10 has a reduced exterior size because asmaller diameter cylinder can be used with the actuator rod, therebyproviding a “low profile” linear actuator assembly. Further, since asubstantive surface length of rod 12 is always in slideable contact withthe inner surface 42 of cylinder 14, as seen in FIG. 4, a maximum lengthof bearing surface to rod diameter ratio is maintained. This low profilelinear actuator assembly also has fewer components, is lighter weight,and is significantly simpler to manufacture, and as a result, is a lessexpensive actuator assembly.

As best seen in FIG. 4, a rear end 50 of the actuator rod 12 thatremains in the cylinder 14 has a seal 54 mounted in an annular groove52. The seal is configured to maintain a fluid-tight seal under thefluid pressures in the cylinder's fluid chamber. The seal slideably andsealably engages the inner surface of the cylinder. In one embodiment,the seal is a Parker Hannifin PolyPak™ seal, although other seals can beused to prevent the pressurized hydraulic or other driving fluid frommoving forwardly past the rear end of the rod. In one embodiment, theseal is pressed into the annular groove during assembly before theactuator rod is inserted into the cylinder. In another embodiment, theseal can be a “formed-in-place” seal, such as a thermoplastic or othersealant that can be injected or otherwise disposed into the annulargroove after the actuator rod is positioned in the cylinder and allowedto cure.

The front end 44 of the actuator rod includes an aperture 56 thatreceives a mounting pin (shown in phantom lines) that mounts to thedevice carrying the linear actuator assembly. The mounting pin allowsthe actuator rod to pivot relative to the mounting pin and/or thedevice, so that the actuator rod and the cylinder remain axially alignedas the actuator rod is moved between the extended and retractedpositions. In this configuration the front mounting pin has dualfunctions. The mounting pin acts as a retaining pin that holds theactuator rod in place relative to the device carrying the linearactuator and relative to the cylinder. The mounting pin also acts as apivot mount that pivotally connects the front of the linear actuatorassembly to the device. In one embodiment, the surface defining theaperture 56 in the front end of the actuator rod is coated or otherwisetreated with a lubricious material, such as the electroless nickelcoating discussed above. In another embodiment, at least a portion ofthe mounting pin is provided with the lubricious coating that engagesthe mounting pin to provide the low friction interface between themounting pin and the actuator rod. This arrangement eliminates the needfor front pivot bushings, thereby further reducing the complexity andcost of the linear actuator assembly.

FIG. 6 is an enlarged cross-sectional view of the front end portion ofthe linear actuator assembly 10 of FIG. 4. In the illustratedembodiment, the cylinder 14 has an interior annular groove 58, and aseal 60 is retained in the annular groove. The seal 60 slideably andsealably engages the outer surface 46 of the actuator rod as theactuator rod moves between the extended and retracted positions. Theseal 60 can be positioned in the annular groove during assembly beforethe actuator rod is inserted into the cylinder. In other embodiments,the seal 60 can be a “formed-in-place” seal, such a thermoplastic orother sealant, that can be injected or otherwise disposed into theannular groove after the actuator rod is positioned in the cylinder andallowed to cure. In the event some fluid leaks forwardly past the seal54 (FIG. 4) over time, the front seal 60 blocks any of the leaked fluidfrom exiting out a front end 66 of the cylinder 14. In the illustratedembodiment, the seal 60 is a resilient, flexible quad-ring, althoughother seals can be used. One of the benefits of being able to use such aseal 60 at the front end portion is that the cylinder can be arelatively thin-walled cylinder, thereby providing a low-profile,durable assembly.

In the illustrated embodiment, an overflow port 62 is provided in thecylinder just rearward of the annular groove. A return tube 64 (shown inphantom lines) can be connected to the overflow port to return any ofthe leaked hydraulic or other driving fluid back to the fluid reservoir.The return tube and the overflow port help ensure that any fluid thatmakes its way to the front end 66 of the cylinder is not forced past theseal 60.

The front end of the cylinder also has a bored interior recess 68, and ascraper ring 70 is retained in the recess. The scraper ring has anangled leading edge portion 72 that rides along the outer surface of theactuator rod to scrape off any dirt, debris, or the like that may havegotten onto the rod when it was in the extended or partially extendedposition. The scraper ring of the illustrated embodiment is constructedof a hard, durable plastic material that will not damage or degrade theouter surface 46 of the actuator rod. Other suitable materials can beused for the scraper ring in other embodiments.

FIG. 7 is a side elevation view of the front end portion of the linearactuator assembly 10 in accordance with another embodiment. FIG. 8 is across-sectional view of the front end portion of the linear actuatorassembly taken substantially along line 8-8 of FIG. 7. The linearactuator assembly 10 of this embodiment has an external shaft sealassembly 74 attached to the front end 66 of the cylinder. As best seenin FIG. 8, the external shaft seal assembly of the illustratedembodiment has a retaining member 82 connected to a seal portion 78 andto a scraper portion 76. Other embodiments of the seal assembly caninclude the seal portion and the retaining member without the scraperportion. The retaining member is configured so it fits over and securelyattaches to the end of the cylinder along the cylinder's exteriorsurface so that the seal portion and the scraper portion are coaxiallyaligned with the cylinder and securely held adjacent to the end of thecylinder. Unlike conventional shaft seals, the external shaft seal canbe assembled to smaller housing features. The retaining member of theillustrated embodiment is a “press-on” retainer that is securely pressfit onto an exterior mounting surface of the cylinder, although othermeans of attachment may be employed. Accordingly, when installed, theinner diameter of the seal assembly substantially corresponds to theouter diameter of the exterior mounting surface of the cylinder.

In the illustrated embodiment, the scraper portion includes a scraperedge 80 positioned forward of the seal portion 78. The scraper portionis a hard plastic ring with an inner diameter that corresponds to theouter diameter of the actuator rod. The seal portion is a spring-loadedlip seal biased radially inwardly to sealably engage the outer surfaceof the actuator rod. Other embodiments may be used. The press-onretaining member of the illustrated embodiment is an annular sheet metalcap that securely retains the scraper portion and seal portion inposition such that the seal assembly can be installed on the end of thecylinder in a single manufacturing step. The seal assembly with thepress-on retaining member is attached to the outside of the cylinder andholds the seal portion immediately adjacent to the end of the cylinder,thereby avoiding the need for an internal bore or groove machined intothe inside surface of the cylinder.

In the illustrated embodiments, the frictional engagement of theexternal shaft seal assembly's press fit connection is such that welds,additional fastening devices or securing mechanisms are not needed. As aresult, the seal assembly can be installed on the cylinder fairlyquickly and easily. The seal assembly can also be pulled off of the endof the cylinder for repair or maintenance. A replacement seal can bequickly installed if needed by press fitting it on the exterior of thecylinder, thereby minimizing the amount of time the actuator assembly isout of service. The retaining member of other embodiments can beconfigured to engage a recess, detent, threads, or other retainingfeature provided on the outer surface at the end of the cylinder.

One of the benefits of this seal assembly arrangement is that the sealassembly allows a larger outside diameter seal to be used at the frontend of the cylinder without requiring that the cylinder have a thickerwall section to accommodate the seal. In the illustrated embodiment, theseal has a thickness approximately the same (or slightly less than) thethickness of the thin-walled cylinder, thereby maintaining a low profileof the assembly. Other embodiments can use a seal portion having adifferent thickness. A further benefit of the seal assembly is that itmounts to an external housing feature, so the entire assembly, orportions of the assembly, can be replaced quickly and easily withouthaving to disassemble any other portion of the linear actuator. Anotherbenefit is that the external shaft seal assembly saves space and reducesthe weight of the components to which it is affixed.

The external shaft seal assembly is described in connection with thecylinder of the linear actuator assembly. The seal assembly can also beconnected to other structures to create a substantially fluid tight sealagainst a shaft. As an example, the seal assembly with the seal portionand the retaining member can be used with bearing assemblies, pumps,motors, gear boxes, rods, cylinders or other shaft structures. The sealassembly attaches to the exterior of a structure and securely holds theseal portion (and scraper portion if provided) immediately adjacent tothe end of the structure and in engagement with the shaft. Accordingly,a wide range of seal portions could be used without requiring a bore orinternal groove within the inside surface of the structure. Accordingly,the structure and shaft assembly can have a lower profile (e.g. areduced outer diameter) because the wall thickness of the structure doesnot have to accommodate the internal bore or groove.

FIG. 9A is an enlarged cross-sectional view of the rear end portion ofthe linear actuator assembly of FIG. 4. In the illustrated embodiment,an end plug 90 is positioned within the interior area 40 of the cylinder14. The end plug 90 can be positioned at least partially within thecylinder, or it can be exterior of the cylinder. FIG. 10 is an enlargedside elevation view of the end plug shown removed from the cylinder ofFIG. 9A. The end plug of the illustrated embodiment is a generallycylindrical member having an outer diameter that approximatelycorresponds to the inner diameter of the cylinder, such that an outersurface 92 of the end plug frictionally engages the inner surface 42 ofthe cylinder in a slip or press fit configuration. The illustrated endplug fits snugly into the end of the cylinder such that a rear face 94of the end plug is substantially co-planar with a rear edge 96 of thecylinder.

The end plug has an aperture 98 coaxially aligned with an aperture 100of substantially the same size formed in the cylinder. In theillustrated embodiment, the end plug is securely retained in thecylinder by the friction fit and then by the mounting pin that extendstherethrough. No additional structures, fasteners, or securing devicesare needed to retain the end plug in position in the cylinder. Thisconfiguration of the end plug with the cylinder and the mounting pin hasa reduced number of parts, is lighter weight, and is easier and fasterto assemble, thereby reducing the manufacturing cost of the linearactuator assembly.

In this arrangement, the rear mounting pin has dual functions. Themounting pin acts as a retaining pin that holds the end plug in placewithin the cylinder. The retaining pin function also holds the rear endportion of the cylinder in place relative to the actuator rod. Themounting pin also acts as a pivot mount that pivotally connects the rearof the linear actuator assembly to the device carrying the linearactuator assembly. This arrangement eliminates the need to weld the endplug into place. Accordingly, the cylinder is not subjected to weldingand the distortion or warping that can be caused by the heat of weldingthereby eliminating the need for re-machining, honing, polishing andother post welding processes to compensate for residual inducedstresses. This arrangement also permits easy and complete disassemblyand reassembly for service or maintenance.

The arrangement of the mounting pins with the linear actuator assemblyalso acts to operatively hold the cylinder and the actuator rod inposition and together when they are mounted on the device carrying thelinear actuator assembly. When the mounting pins are removed, theactuator rod and cylinder can be pulled apart from each other. The othercomponents of the linear actuator can then be accessed, disassembled,removed, or replaced.

The aligned apertures 98 and 100 pivotably receive a mounting pin 26(shown in phantom lines) to allow the rear end portion of the linearactuator assembly to pivot relative to the device carrying the linearactuator assembly. The interior surface of the end plug defining theaperture can be coated with a lubricious material to facilitate thepivoting movement of the mounting pin as the actuator rod moves betweenthe extended and retracted positions. In yet another embodiment, themounting pin can be provided with a lubricious material or coatingthereon so as to provide a low friction interface between the end plugand the mounting pin. In another embodiment, both the end plug and themounting pin can be provided with the lubricious material or coating.This configuration eliminates the need for rear cylinder bushings whileproviding a corrosion resistant, low friction interface. Accordingly,the linear actuator assembly has fewer parts, is less complex, easier toassemble and less expensive to manufacture than the prior art.

As best seen in FIG. 9A, a forward portion 102 of the end plug is spacedapart from the rear end portion 50 of the actuator rod to define a fluidchamber 108 that contains the driving fluid used to drive the actuatorrod. The front end portion of the end plug includes an annular groove104 that contains a seal 106. The seal sealably engages the innersurface 42 of the cylinder to prevent the pressurized driving fluid frommoving rearwardly past the seal. In the illustrated embodiment, the seal106 is a Parker Hannifin PolyPak™ seal, although other seals could beused in other embodiments. The seal 106 could also be a“formed-in-place” seal, such as a thermoplastic or other sealant, thatcan be injected or otherwise disposed into the annular groove after theend plug is positioned in the cylinder.

The fluid chamber 108 is in fluid communication with a hydraulic orpneumatic power source via a passageway 110 extending through the endplug. The end plug contains valves in the passageway that control fluidflow into or out of the fluid chamber 108 (FIG. 9A). The passageway ofthe illustrated embodiment includes a first portion 112 formed by acontoured through hole that extends substantially perpendicular to theend plug's longitudinal axis. A second portion 114 of the passagewayextends forwardly from the first portion parallel with the end plug'slongitudinal axis and terminates at a port 111 in fluid communicationwith the fluid chamber. Each of the first and second portions of thepassageway may contain a valve or valves that control the flow ofhydraulic or other driving fluid to and from the fluid chamber (FIG.9A).

In the illustrated embodiment, the first portion of the passageway isaligned with apertures in the cylinder and includes a connection port116 that removably and sealably retains a connection fitting 118. Theconnection fitting is coupled to a fluid line 120 that carries the fluidto and from a power source (FIG. 4). In the illustrated embodiment, thehydraulic power source includes a tank 121 or other fluid reservoir, apump 129 and a valve assembly 123. Referring back to FIG. 9A, theconnection fitting 118 can have external threads that engage internalthreads within the connection port. An O-ring seal 119 is provided toprevent leakage of the fluid between the connection fitting and theconnection port. The connection fitting sealably engages a lower portionof a valve assembly 122 that extends into the end plug through thepassageway's first portion opposite the connection port. The valveassembly has a controllable valve member 126 disposed in the firstportion of the passageway. The valve member is adjustable to control theflow rate of fluid through the end plug and into or out of the fluidchamber. By providing control valves within the linear actuator,response time is greatly improved, as compared to actuators of the priorart, where controls valves are some distance away from the actuator.This is because response time is adversely affected by thecompressibility of the fluid volume contained within the fluid conduits,between the control valves and the actuator, and the elasticity of theconduits themselves. Accordingly, this valve arrangement substantiallyeliminates lost motion and/or actuator function delay due to fluidcompressibility and conduit elasticity.

In the illustrated embodiment, the valve assembly is a solenoid valveassembly, although other valve assemblies could be used in otherembodiments. The lower portion of the valve assembly of the illustratedembodiment has external threads that engage internal threads within theend plug. Accordingly, the valve assembly can be easily and quicklyattached to the cylinder and the end plug, thereby reducing themanufacturing cost of the linear actuator assembly.

As indicated above, the illustrated actuator is a ram-type actuator,wherein the fluid is driven into the fluid chamber 108 through thepassageway 110 in the end plug, and the fluid drives the actuator rodforwardly toward the extended position. The actuator rod returns underthe force of gravity along a return stroke back toward the retractedposition, so long as the valve assembly allows for the reverse flow ofthe hydraulic fluid back through the connection fitting and the fluidline. The speed of the actuator rod on the return stroke is limited by arestrictor valve assembly 134 positioned within the second portion ofthe passageway in the end plug. The restrictor valve assembly allows thefull flow into the fluid chamber, while restricting the flow of fluidout of the fluid chamber, thereby restricting the speed at which theactuator rod can return to the retracted position.

The restrictor valve assembly illustrated in FIG. 9A is contained in anenlarged valve chamber 136 of the passageway's second portion forward ofa narrower passageway segment 115 that connects to the passageway'sfirst portion. The restrictor valve assembly includes a valve poppet 138axially movable within the valve chamber, and a biasing member 140 ispositioned within the valve chamber. The biasing member engages thepoppet to urge the poppet rearwardly toward a closed position. In theclosed position the poppet is in sealable engagement with a shoulder 142defined at the transition between the valve chamber and the narrowerpassageway segment. In the illustrated embodiment, the biasing member isa coil spring, although other biasing devices can be used in otherembodiments. A spring clip 144 is mounted in the forward area of thevalve chamber and positioned to provide a surface against which thebiasing member can press to react the biasing force exerted against thepoppet 138.

FIG. 11 is an enlarged isometric view of the poppet 138 of therestrictor valve assembly shown removed from the end plug of FIG. 9A.The poppet has a central orifice 146 therethrough that allows a smallflow of fluid to pass through the poppet even when the poppet is in theclosed position. The outer portions of the poppet include four outerflow path portions 148 around the perimeter. The flow path portions aresymmetrically disposed around the poppet. In the illustrated embodiment,the flow path portions have an arcuate shape and each flow path portionis opposite another one of the flow path portions. The poppet in otherembodiments can have other shapes and configurations.

The poppet of the illustrated embodiment has a maximum diameter slightlyless than the inner diameter of the valve chamber (FIG. 9A) such thatthe poppet can move axially within the valve chamber between closed andopen positions. The distance between the opposing flow path portions,however, is greater than the diameter of the narrower passageway segmentof the flow path's second portion. Accordingly, when the poppet is in aclosed position (FIG. 9A) and pressed against the shoulder, the flowpath portions are radially outward of the opening to the narrowerpassageway segment, so fluid cannot flow rearwardly around the flow pathportions and into the narrower passageway segment. The only flow offluid rearwardly from the fluid chamber 108 through the restrictor valveis through the small central orifice in the poppet and into the narrowerpassageway segment. Accordingly, the small central orifice in the poppetlimits the rearward flow of fluid, thereby limiting the speed at whichthe actuator rod can return toward its retracted position.

FIG. 12 is a cross-sectional view of the rear end portion of the linearactuator assembly with the restrictor valve assembly 134 in the openposition. As the hydraulic fluid is directed forwardly through thepassageway's second portion, the fluid presses forwardly against thepoppet 138 so as to compress the biasing member 140 and move the poppetaway from the shoulder 142. The poppet's flow path portions allow a flowof the fluid to pass through the valve chamber and around the poppettoward the fluid chamber 108. The two pairs of opposing flow pathportions are configured such that the poppet is hydraulically balancedas the fluid flows around the symmetrically disposed flow path portions,so the poppet maintains axial alignment within the valve chamber whilemoving to or from the open position. As a result, the restrictor valveassembly provides a simple valve mechanism that effectively andaccurately controls flow of the fluid into and out of the fluid chamber,thereby controlling the position and speed of the actuator rod'smovement relative to the cylinder.

Referring back to FIG. 4, Pump 129 draws fluid from reservoir 121 anddelivers the fluid via conduit 125 to valve (or valves) 123 throughconduit 120 to linear actuator 10, while blocking any connection toconduit 127. This fluid from conduit 120, extends rod 12. To retract rod12, via gravity or some other mechanical force, valve (or valves) 123blocks fluid from pump 129, while opening a connection between conduits120 and 127 back to tank 121. The valves 123 can be contained in amanifold assembly on a vehicle carrying the linear actuator assembly. Inone embodiment, the valves 123 can be configured to control, as anexample, fluid pressure, flow rate, and/or flow direction of the drivingfluid. The valve manifold assembly on the vehicle can be mounted remotefrom the linear actuator assembly and coupled thereto by the fluidlines. The valves 123 are coupled to a control system that includes acontroller, such as a joystick, that an operator can use to control thevalves, thereby controlling the resulting movement of the linearactuator assembly.

FIG. 9B is an isometric view of a rear end portion of a linear actuatorassembly in accordance with another embodiment. FIG. 9C is across-sectional view of the rear end portion of the linear actuatorassembly taken substantially along lines 9C-9C of FIG. 9B. FIG. 9D is anisometric view of the end plug shown removed from the cylinder of thelinear actuator assembly of FIG. 9C. The end plug 900 is similar to theend plug 90 discussed above except the plurality of control valves 902are contained in the end plug or connected to the end plug and containedwithin the cylinder adjacent to the end plug. The control valves areconfigured to control at least fluid pressure, flow rate, and direction.Accordingly, all of the valves used to control movement of the linearactuator assembly are contained in the end plug or in the cylinderadjacent to the end plug.

In the illustrated embodiment, the valves 902 are coupled to a fluidsupply line 904 and a fluid return line 906, both of which are coupledto a remote tank 908. In the case where the linear actuator is apneumatic device, line 904 would be coupled to a compressed air powersource, and line 906 would be coupled to an exhaust. The fluid supplyline 904 is connected to an inlet fitting 910 that extends into the endplug and sealably engages a first portion 914 of a valve housing 912(FIG. 9C) within the end plug. The first portion of the valve housing isin fluid communication with the fluid chamber 108 via the second portion114 of the fluid passageway discussed above. The fluid return line isconnected to a return line fitting 916 that extends into the end plugand sealably engages a second portion 918 of the valve housing (FIG.9C). The second portion of the valve housing is also in fluidcommunication with the fluid chamber via the second portion of the fluidpassageway discussed above.

As best seen in FIG. 9D, the end plug of the illustrated embodiment alsocontains one or more solenoid valve assemblies 920 mounted in aperturesformed in the end plug. The illustrated solenoid valve assemblies 920are also in fluid communication with the valve housing (FIG. 9C) andconfigured to control the direction, flow rate, and/or pressure of thefluid moving through the valve housing to or from the fluid chamber. Thesolenoid valve assemblies are connected to an electrical controller viawires 922 that extend through wire grommets 924, although otherelectrical configurations can be used in other embodiments. The valvehousing contains the valves needed to control the fluid (e.g., flowrates, flow direction, pressure, etc.) for operation of the linearactuator assembly such that all the valves are fully contained in theend plug. As a result, the actuator rod will move or otherwise reactsubstantially instantaneously upon activating or adjusting the valves,with no time delay or lag, because the effects of fluid compressibilityand componentry elasticity (particularly in hoses and lines connected toremotely located valves) are virtually eliminated. This arrangementprovides intrinsic, partial, or complete control of cylinderfunctionality.

The end plug 900 with the valves 902 contained therein is removable as aunit from the rear end portion of the cylinder. This arrangement of thevalves in the end plug greatly aids in system troubleshooting, becauseeach cylinder contains its own controls. If any of the valves needmaintenance or replacement, the fluid supply and return lines 904 and906 can be disconnected and the end plug assembly with the end plug andintegral control valves can be removed as a unit and replaced with a newor different end plug assembly. This replacement of the end plug resultsin very little downtime for the vehicle, and the replacement process isnot labor-intensive. The removed end plug assembly can then be servicedin due course without having to keep the vehicle out of service.

Another benefit of having the control valves in the end plug is that anoperator can quickly and easily troubleshoot and diagnose a situation ifa problem occurs with a linear actuator assembly on a vehicle havingmultiple linear actuator assemblies. Prior art systems often use acomplex valve manifold located remote from the conventional linearactuators, and the manifold contains all the valves that control thelinear actuators. If any of the multiple linear actuators malfunction,the diagnosis process can be very time-consuming, complex, andlabor-intensive. The arrangement in the current embodiments with the endplug and integral control valves avoids the diagnosis complexitiesbecause the manifold is eliminated and all of the valves for each linearactuator are contained in that assembly's end plug. Any problem with alinear actuator's valves can be diagnosed by going directly to thelinear actuator assembly at issue and troubleshooting the problem forthat particular linear actuator.

FIG. 13 is an isometric view of a two-way linear actuator assembly 160in accordance with another embodiment. FIG. 14 is a cross-sectional viewof the linear actuator assembly of FIG. 13 taken substantially along thelines 14-14. The illustrated linear actuator assembly 160 utilizes fluidpressure to drive an actuator rod 162 in two directions, toward theretracted position (shown in FIG. 13) and toward the extended position.The linear actuator assembly includes a cylinder 164 that defines aninterior area 165 and is similar to the cylinder 14 discussed above. Thecylinder 164 of the illustrated embodiment is also a cylinder asdiscussed above made of metal or other suitable materials to withstandthe operating pressures of the two-way linear actuator assembly. None ofthe linear actuator assembly's components are welded together during theassembly process.

The cylinder and the actuator rod have substantially the sameconstruction as described above except that the cylinder's innerdiameter is larger than the outer diameter of the actuator rod. As bestseen in FIG. 14, a piston 166 is securely attached to a rear end portion168 of the actuator rod such that the piston divides the interior areainto front and rear fluid chambers 171 and 173. The outer surface of thepiston sealably and slideably engages an inner surface 167 of thecylinder such that the driving fluid is substantially restricted fromflowing past the piston between the front and rear fluid chambers.Accordingly, the actuator rod is moved toward the extended position bydirecting the hydraulic or pneumatic fluid into the rear fluid chamber,while exhausting fluid from the front fluid chamber. The actuator rod ismoved toward the retracted position by directing the fluid into theforward fluid chamber, while exhausting fluid from the rear chamber.

The linear actuator assembly has an end plug 170 that extends into therear end portion of the cylinder similar to the end plug discussedabove. The end plug 170 includes an annular groove 172 that contains aseal 174 that prevents the pressurized fluid within the rear fluidchamber from passing between the cylinder and the end plug. The seal 174can be a unit pressed into the annular groove before the end plug isinserted into the cylinder, or the seal can be a “formed-in-place” sealinjected or otherwise disposed into the annular groove after the endplug is positioned in the cylinder, as discussed above.

The end plug 170 of the illustrated embodiment includes a protrudingconnection portion 176 that extends beyond the rear end portion of thecylinder. The protruding portion has an aperture 178 that pivotablyreceives the mounting pin 26 (shown in phantom lines in FIG. 14). Inanother embodiment, the end plug can have the same configuration as theend plug 90 discussed above wherein the entire end plug is containedwithin the rear end portion of the cylinder and coaxially alignedapertures in the end plug and the cylinder receive the mounting pin. Asindicated above, the surface defining the aperture in the end plug canbe coated with the lubricious material. The mounting pin can also beprovided with a coating or layer of the lubricious material, therebyproviding a low friction interface between the components whileeliminating the need for rear cylinder pivot bushings. The end plug caninclude a fluid passageway therethrough coupled to fluid conduit linesand a power source and configured to direct hydraulic or other drivingfluid into and out of the fluid chambers. In another embodiment, the endplug includes the interior valve assemblies as discussed above thatcontrol the flow rate, pressure, and/or direction of the hydraulic fluidinto and out of the fluid chambers. Other embodiments can use otherfluid lines and valve configurations for the passage of the fluid intoand out of the cylinder.

The linear actuator assembly of the illustrated embodiment includes afront end cap 181 attached to the exterior of the cylinder's forwardportion 182, and a front gland 180 positioned in the interior area atthe cylinder's forward portion 182. The end cap acts as a retainingdevice to contain the front gland in the cylinder. The end cap 181 ofthe illustrated embodiment has internal threads 183 (FIG. 14) that matewith external threads 185 on the cylinder's forward portion.Accordingly, the threaded end cap can be easily removed from thecylinder to access the front gland, such as for maintenance orinspection. Other embodiments can use other securing means for retainingthe end cap on the cylinder.

The front gland 180 has an outer diameter that corresponds with theinner diameter of the cylinder, such that the front gland can fit intoand frictionally engage the inside surface of the cylinder. The frontend of the gland includes a lip 187 that contacts the forward edge ofthe cylinder and prevents the gland from sliding too far into thecylinder. The end cap securely holds the lip against the forward edge ofthe cylinder. A rear portion 184 of the front gland has an annulargroove 186 that contains a seal 187 therein that sealably engages theinside surface of the cylinder. The seal of the illustrated embodimentis a Parker Hannifin PolyPak™ seal configured to maintain a seal underthe fluid pressures within the cylinder, although other embodiments canuse different seals. For example, the seal 187 in other embodiments canbe a formed-in-place seal, as discussed above.

The front gland 180 has a fluid passageway 188 in fluid communicationwith an aperture 190 formed in the forward portion of the cylinder. Thefluid passageway and the aperture are in fluid communication with thefront fluid annulus chamber 191 and positioned to allow the drivingfluid to move into or out of the forward fluid chamber 171.

In one embodiment, not shown, a front portion of the front glandincludes an annular groove containing a seal that sealably engages theinner surface of the cylinder. Forward of the seal is a retention ringthat securely engages the front gland and a retaining groove formed inthe inner surface of the cylinder. The retention ring locks the frontgland in position within the cylinder and prevents axial movement of thegland during operation of the linear actuator assembly.

The actuator rod extends through and is slideably disposed through anelongated hole 196 in the front gland. The elongated hole has an innerdiameter that corresponds with the outside diameter of the actuator rodsuch that the outer surface of the actuator rod slideably engages thesurface of the front gland defining the elongated hole. The actuator rodof the illustrated embodiment is provided with a lubricious surface(such as a lubricious material discussed above) that provides alow-friction engagement between the actuator rod and the front gland.The lubricious surface of the actuator rod acts as a low-frictionbearing surface that supports the actuator rod during movement betweenthe extended and retracted positions. In another embodiment, the frontgland can be provided with a lubricious coating or the like that engagesthe actuator rod sliding through the front gland. This arrangement withthe coating of lubricious material on the surface of the actuator rodand/or the inner surface of the gland eliminates the need for a frontgland bushing for dual direction cylinders. Accordingly, the linearactuator assembly of the illustrated embodiment has fewer parts, is lesscomplex, is easier to assemble, has a lower profile, is lighter weight,is corrosion-resistant, and is less expensive to manufacture than theprior art.

The front portion of the gland has an annular groove 200 extendingaround the elongated hole 196. A seal 202 is contained in the annulargroove and sealably and slideably engages the actuator rod 162 andprevents fluid from exiting the forward fluid chamber through theelongated hole 196. The end cap contains a scraper assembly 206 thatengages the surface of the actuator rod during movement between theextended and retracted positions.

The actuator rod has a forward portion 208 that extends forwardly out ofthe front gland and is exterior of the cylinder. In one embodiment (notshown in FIG. 14), the forward portion of the actuator rod includes anaperture that receives a mounting pin, substantially as discussed above.In the illustrated embodiment of FIG. 14, the forward portion of theactuator rod has a domed end surface 210 and a hole 212 extendingthrough the actuator rod adjacent to the domed end surface. In theillustrated embodiment, the domed end surface is a convex shape, such asa substantially semi-spherical shape, although other curved or contouredsurfaces can be used.

As best seen in FIGS. 14 and 15, the actuator rod's forward portion 208and the domed end surface 210 extend into a receiving pocket 214 formedin a self-aligning coupler 216. The receiving pocket has a concaveportion, such as a substantially semi-spherical shape, that generallycorresponds to the shape of the actuator rod's convex portion so as toallow some pivotal motion between the self-aligning coupler and theactuator rod's domed end surface. The self-aligning coupler is pivotallyconnected to the actuator rod's forward portion by a pin 220 thatextends through axially aligned holes in the coupler and the actuatorrod, although other attachment mechanisms could be used in otherembodiments.

The pin of the illustrated embodiment is press fit into the actuator rodso the pin does not move relative to the actuator rod. The holes in theself-aligning coupler, however, have a slightly larger diameter than thepin, so the self-aligning coupler can pivot about the pin in at leastone plane relative to the end of the actuator rod. As seen in FIG. 15,in one embodiment, the holes in the self-aligning coupler are sized tobe larger than the pin's outer diameter so that the coupler can move inmultiple planes relative to the end of the actuator rod. In anotherembodiment, the pin can be press fit into the holes in the self-aligningcoupler. The hole through the actuator rod has a larger diameter thanthe pin so the pin and self-aligning coupler can pivot and move relativeto the end of the actuator rod in one plane or in multiple planes.

The self-aligning coupler includes an aperture 222 forward of thereceiving pocket that pivotally receives the mounting pin 26 (shown inphantom lines) that connects to the device carrying the linear actuatorassembly. The self-aligning coupler interconnects the actuator rod andthe mounting pin such that the coupler will allow for some pivotalmotion of the coupler relative to the mounting pin during operation ofthe linear actuator assembly. The self-aligning coupler requires lessspace than conventional alignment devices at least in part because therelative motion is between the coupler and the actuator rod in multipleplanes. Accordingly, the end of the actuator rod effectively becomespart of the self-aligning coupling arrangement. This orientation andmovement of the self-aligning coupler helps maintain axial alignment ofthe cylinder and the actuator rod, thereby alleviating binding issuesassociated with pivot mounts rigidly affixed to the actuator rod.Accordingly, the configuration of the self-aligning coupler preventsand/or reduces stress, excessive wear, and poor performance experiencedby conventional linear actuators because of misalignment of thecomponents during assembly or installation. Also, the configuration ofthe self-aligning coupler of the illustrated embodiment isuncomplicated, requires fewer parts, and is less expensive than priorart alignment systems. The resulting linear actuator assembly is asimple construction that does not sacrifice performance to achieve thesimpler and less expensive linear actuator.

FIG. 16 is a cross-sectional view of a linear actuator assembly 160 withformed-in-place seals in accordance with another embodiment. In thisembodiment, the inner surface of the cylinder adjacent to the end plugincludes a rear annular groove 226 radially aligned with the annulargroove 172 in the end plug 170. The cylinder also has one or moreinjection apertures 228 in communication with the cylinder's rearannular groove and the end plug's annular groove when the end plug is inposition in the cylinder. Uncured thermal plastic or other suitableflowable sealing material is injected or otherwise directed through theinjection apertures so as to fill the annular space defined by themating annular grooves. The seal material is allowed to cure or set up,thereby providing a formed-in molded seal that sealably fills andengages the mating annular grooves around the entire end plug. In otherembodiments, multiple injection apertures can be used to facilitate theinjection and formation of the seals.

The cylinder of the illustrated embodiment also includes an annulargroove 232 formed adjacent to a mating groove 234 in the front glandwhen the front gland is positioned in the front end portion of thecylinder. A plurality of injection apertures 228 are in communicationwith the mating annular grooves. Sealing material, such as an uncuredthermal plastic material is pressure injected through the injectionapertures to fill the space defined by the mating grooves 232 and 234,thereby forming a seal 236 between the front gland and the cylinder. Asimilar configuration for forming other seals can be provided in otherembodiments by incorporating grooves in the inner surface of thecylinder with grooves in the front gland or the end plug and dispensinguncured material, such as thermal plastic or other material, therein andallowing the material to cure so as to form the seal that adheres to allcontacted surfaces.

When cured, the seal forms a permanent seal that crosses over theannular interface between the inner surface of the cylinder and outersurface of the end plug or front gland or other member. The curedmaterial can act to resist movement of the end plug and/or the frontgland within the cylinder. The resulting formed-in-place seals provideseveral benefits over conventional seals. For example, theformed-in-place seals can be formed at a lower cost than conventionalseals. In static applications of the formed-in-place seals, surfacefinish is not a factor for mating seal surfaces. Also, theformed-in-place seals have a higher degree of reliability compared toconventional seals, particularly in static applications.

The formed-in-place seals of the illustrated embodiment are configuredso that they do not irreleaseably lock the end plug or front gland inthe cylinder. The end plug or front gland can still be removed from thecylinder, although the seal will be destroyed. The destroyed sealmaterial can be cleaned out of the annular grooves and a replacementseal can be formed in place after the end plug or front gland isinserted back into the cylinder. In another embodiment, the seal isconfigured to act as a locking device that fixedly retains the end plugor front gland in place in the cylinder. It is noted that in otherembodiments, the use of the injected seal material is not limited tostatic sealing. By matching a singular groove to a release coatedstraight bore, a dynamic seal can be created between two components withimproved performance reliability and lower cost for wide-rangingapplications.

FIG. 17 is an isometric view of a vehicle 300 having a plurality oflinear actuator assemblies 302 in accordance with an embodiment of thepresent invention. The vehicle 300 of the illustrated embodiment is apersonnel lift having a body 304 mounted to a chassis 306, a proximalboom arm 308, an intermediate boom arm 310, and a distal boom arm 312. Apersonnel basket 314 is attached to the end of the distal boom arm. Eachof the actuator assemblies 302 can have a construction similar to atleast one of the linear actuator assemblies described above.

In the illustrated embodiment, the linear actuator assemblies 302 have aconstruction similar to the assemblies discussed above and illustratedin FIGS. 9B, 9C, and 9D, wherein the valves used to control movement ofthe assembly are contained in the end plug in the cylinder. Accordingly,the vehicle does not need (or include) a conventional complex valvemanifold coupled to the body and remote from the linear actuatorassemblies. Instead, the fluid supply and return lines 125 and 127 areconnected to the linear actuator assemblies. The fluid supply and returnlines can have segments daisy-chained together in series or in paralleldepending on the configuration needed for movement of the boom armsand/or the personnel basket.

One of the benefits of this vehicle configuration is that thearrangement of fluid lines in greatly simplified and there issubstantially no time delay in moving the actuator rod in response to anoperator moving a joystick or other controller. This configurationeliminates the significant time delays that can occur because of thetime needed for line pressurization and line swelling that can occur inflexible fluid lines when the valve manifold is remote from the linearactuators. Unlike the prior art, the linear actuator assemblies of theillustrated embodiment with the control valves in the end plug move assoon as the valves are activated in response to the operator's movementof the joystick or other controller. The result is very responsivelinear actuator assemblies, thereby providing a very responsivepersonnel lift or other vehicle or machine.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A linear actuator assembly connectable to first and second mountingportions, the first mounting portion being moveable relative to thesecond mounting portion, comprising: a cylinder body having an interiorarea and a rear end portion positionable adjacent to the second mountingportion; an actuator rod slideably disposed in the cylinder body, theactuator rod having a forward end portion exterior of the cylinder bodyand positionable adjacent to the first mounting portion; an end plugpositioned at least partially within the rear end portion of thecylinder body, the end plug closing the rear end portion of the cylinderbody; a first retaining member coupled to the forward end portion of theactuator rod and being connectable to the first mounting portion toallow the actuator rod to pivot about the first retaining memberrelative to the first mounting portion; and a second retaining memberremovably engaging the end plug and the rear end portion of the cylinderbody, the second retaining member being connectable to the secondmounting portion to allow the cylinder body to pivot about the secondretaining member relative to the second mounting portion, and the secondretaining member retaining the end plug within the rear end portion ofthe cylinder, wherein the end plug can be slideably removed from thecylinder body upon disengagement of the second retaining member from theend plug.
 2. The assembly of claim 1 wherein the second retaining memberextends through the end plug and the rear end portion of the cylinderbody.
 3. The assembly of claim 1 wherein the second retaining member isa mounting pin extending through the end plug and the rear end portionof the cylinder body.
 4. The assembly of claim 1 wherein connection ofthe first retaining member to the first mounting portion and connectionof the second retaining member to the second mounting portion hold theactuator rod and cylinder body together and prevent the actuator rodfrom sliding axially out of the cylinder.
 5. The assembly of claim 1wherein the actuator rod is restricted from separating from the cylinderbody when the first retaining member is connected to the first mountingportion and when the second retaining member is connected to the secondmounting portion, and the actuator rod being free to slide out of thecylinder body when the first retaining member is disconnected from thefirst mounting portion and when the second retaining member isdisconnected from the second mounting portion.
 6. The assembly of claim1, further comprises a self-aligning coupler pivotally connected to theforward end portion of the actuator rod and being pivotably moveablerelative to the actuator rod in a plurality of planes, the firstretaining member engaging the self-aligning coupler.
 7. The assembly ofclaim 1, further comprises a self-aligning coupler pivotably connectedto the forward end portion of the actuator rod and being moveablerelative to the forward end portion of the actuator rod in a pluralityof planes, and the first retaining member is connected to theself-aligning coupler.
 8. The assembly of claim 1 wherein the end plughas an aperture therein defined by an interior surface of the end plug,the second retaining member being removably positioned in the aperture,at least one of the second retaining member and the interior surfacehaving a lubricious coating that provides a lubricious interface betweenthe retaining member and the interior surface of the end plug.
 9. Theassembly of claim 1 wherein the end plug has an aperture therein definedby an interior surface of the of the end plug, the second retainingmember being removably positioned in the aperture, at least one of thesecond retaining member and the interior surface being impregnated witha lubricious coating that provides a lubricious interface between thesecond retaining member and the interior surface of the end plug. 10.The assembly of claim 1 wherein the first retaining member is a mountingpin extending through the forward end portion of the actuator rod. 11.The assembly of claim 1, wherein the forward end of the actuator rod hasan aperture therein defined by an interior surface, the first retainingmember being removably positioned in the aperture, at least one of thefirst retaining member and the interior surface having a lubriciouscoating that provides a lubricious interface between the first retainingmember and the interior surface of the actuator rod.
 12. The assembly ofclaim 1 wherein the forward end of the actuator rod has an aperturetherein defined by an interior surface, the first retaining member beingremovably positioned in the aperture, at least one of the firstretaining member and the interior surface being impregnated with alubricious coating that provides a lubricious interface between thefirst retaining member and the interior surface of the end plug.
 13. Theassembly of claim 1 wherein at least one of the first retaining memberand the first mounting portion has a lubricious coating that provides alubricious interface therebetween.
 14. The assembly of claim 1 whereinthe end plug contains a plurality of control valves operable to controlmovement of the actuator rod relative to the cylinder body.
 15. Theassembly of claim 1 wherein the cylinder body has an exterior surface,and further comprising an external shaft seal assembly connect to anexterior surface of the cylinder body and sealably engaging the actuatorrod.
 16. The assembly of claim 1, further comprising a formed-in-placeseal engaging the end plug and the cylinder body.
 17. A linear actuatorassembly connectable to first and second mounting portions, the firstmounting portion being moveable relative to the second mounting portion,comprising: a cylinder body having an interior area and a rear endportion positionable adjacent to the second mounting portion; anactuator rod moveably disposed in the cylinder body, the actuator rodhaving a forward end portion exterior of the cylinder body andpositionable adjacent to the first mounting portion; an end plugconnected to the rear end portion of the cylinder body, the end plughaving a weldless interface with the cylinder body and closing the rearend portion of the cylinder body; a first retaining member coupled tothe forward end portion of the actuator rod and being connectable to thefirst mounting portion to allow the actuator rod to pivot about thefirst retaining member relative to the first mounting portion; and asecond retaining member removably engaging the end plug and beingconnectable to the second mounting portion to allow the cylinder body topivot about the second retaining member relative to the second mountingportion, wherein the end plug can be removed from the cylinder body. 18.The assembly of claim 17 wherein the second retaining member extendsthrough the end plug and the rear end portion of the cylinder body. 19.The assembly of claim 17 wherein the second retaining member is amounting pin extending through the end plug and the rear end portion ofthe cylinder body.
 20. The assembly of claim 17 wherein the end plug isat least partially within the rear end portion of the cylinder.
 21. Theassembly of claim 17 wherein the end plug directly engages the insidesurface of the cylinder.
 22. The assembly of claim 17 wherein connectionof the first retaining member to the first mounting portion andconnection of the second retaining member to the second mounting portionhold the actuator rod and cylinder body together and prevent theactuator rod from sliding axially out of the cylinder.
 23. The assemblyof claim 17 wherein the actuator rod is restricted from separating fromthe cylinder body when the first retaining member is connected to thefirst mounting portion and when the second retaining member is connectedto the second mounting portion, and the actuator rod being free to slideout of the cylinder body when the first retaining member is disconnectedfrom the first mounting portion and when the second retaining member isdisconnected from the second mounting portion.
 24. The assembly of claim17 wherein the end plug has an aperture therein defined by an interiorsurface of the of the end plug, the second retaining member beingremovably positioned in the aperture, at least one of the secondretaining member and the interior surface having a lubricious coatingthat provides a lubricious interface between the retaining member andthe interior surface of the end plug.
 25. The assembly of claim 17wherein the end plug includes a plurality of control valves operable tocontrol movement of the actuator rod relative to the cylinder body. 26.An articulatable assembly, comprising: first and second membersarticulatable relative to each other, the first member having a firstmounting portion and the second member having a second mounting portion;and an actuator assembly connected to the first and second members, theactuator assembly comprising: a cylinder body having an interior area; ashaft disposed in the cylinder body, the shaft having a free end portionexterior of the cylinder body; an end plug removably connected to thecylinder body and closing a portion of the interior area; a firstretaining member coupled to the free end portion of the shaft andconnected to the first mounting portion and configured to allow theshaft to pivot relative to the first mounting portion about alongitudinal axis of the first retaining member; and a second retainingmember removably retaining the end plug in the portion of the cylinderbody, the second retaining member being connected to the second mountingportion and configured to allow the cylinder body to pivot relative tothe second mounting portion about a longitudinal axis of the secondretaining member, wherein the end plug can be removed from the portionof the cylinder body upon disengaging the second retaining member fromthe end plug.
 27. The assembly of claim 26 wherein the second retainingmember extends through the end plug and the portion of the cylinderbody.
 28. The assembly of claim 26 wherein the end plug has a firstaperture and the cylinder body has a second aperture coaxially alignedwith the first aperture when the end plug is in the portion of thecylinder body, and the second retaining member extends through the firstand second apertures to releasably lock the end plug in the portion ofthe cylinder body.
 29. The assembly of claim 26 wherein the secondretaining member is a mounting pin extending through the end plug andthrough the portion of the cylinder body.
 30. The assembly of claim 26wherein a connection of the first retaining member to the first mountingportion and a connection of the second retaining member to the secondmounting portion hold the shaft and cylinder body together and preventthe shaft from sliding axially out of the cylinder.
 31. The assembly ofclaim 26 wherein the shaft is restricted from separating from thecylinder body when the first retaining member is connected to the firstmounting portion and when the second retaining member is connected tothe second mounting portion, and the shaft being separable from thecylinder body when the first retaining member is disconnected from thefirst mounting portion or when the second retaining member isdisconnected from the second mounting portion.
 32. The assembly of claim26, further comprises a self-aligning coupler pivotally connected to thefree end portion of the shaft and being pivotably moveable relative tothe shaft in a plurality of planes.
 33. The assembly of claim 26 whereinthe end plug has an aperture therein defined by an interior surface ofthe of the end plug, the second retaining member being removablypositioned in the aperture, at least one of the second retaining memberand the interior surface having a lubricious coating that provides alubricious interface between the retaining member and the interiorsurface.
 34. The assembly of claim 26 wherein the first retaining memberis a mounting pin extending through the free end portion of the shaft.35. The assembly of claim 26 wherein the free end of the shaft has anaperture therein defined by an interior surface, the first retainingmember being removably positioned in the aperture, at least one of thefirst retaining member and the interior surface having a lubriciouscoating that provides a lubricious interface between the first retainingmember and the interior surface.
 36. The assembly of claim 26 whereinthe end plug contains a plurality of control valves operable to controlmovement of the shaft relative to the cylinder body.
 37. The assembly ofclaim 26 wherein the end plug contains a plurality of control valvesoperable to control movement of the shaft relative to the cylinder body,the end plug and the control valves are removable from the cylinder bodyas a unit.
 38. The assembly of claim 26 wherein the cylinder body has anexterior surface, and further comprising an external shaft seal assemblyconnect to an exterior surface of the cylinder body and sealablyengaging the shaft.
 39. The assembly of claim 26, further comprising aformed-in-place seal engaging the end plug and the cylinder body.
 40. Avehicle, comprising: a vehicle body; first and second members coupled tothe vehicle body and being articulatable relative to each other, thefirst member having a first mounting portion and the second memberhaving a second mounting portion; and an actuator assembly connected tothe first and second members, the actuator assembly comprising: acylinder body having an interior area; a shaft disposed in the cylinderbody, the shaft having a free end portion exterior of the cylinder body;an end plug removably connected to the cylinder body and closing aportion of the interior area; a first retaining member coupled to thefree end portion of the shaft and connected to the first mountingportion and configured to allow the shaft to pivot relative to the firstmounting portion about a longitudinal axis of the first retainingmember; and a second retaining member removably retaining the end plugin the portion of the cylinder body, the second retaining member beingconnected to the second mounting portion and configured to allow thecylinder body to pivot relative to the second mounting portion about alongitudinal axis of the second retaining member, wherein the end plugcan be removed from the portion of the cylinder body upon disengagingthe second retaining member from the end plug.